Noctis

Noctis is all shades of awesome. It mathemagically generates a universe of eight billion solar systems, of which you can fly around in your StarDrifter spacecraft. You can land on planets, check out the scenery, and if you're lucky you'll even find signs of life. You might even find some ruins in your travels -- ruins of the non-Euclidean type....

The interface is hideous, the graphics are minimal, there's no real point to the game, and yet I sank a whole Sunday into it. And I'm a pretty busy guy.

Link. Head to the last page to make sure you get the latest version.